Thermally developable light-sensitive element

ABSTRACT

A lightsensitive element for heat development comprising a support having at least one layer thereon comprising; A. SILVER LAURATE OR SILVER CAPRATE, B. A CATALYTIC AMOUNT OF A PHOTOSENSITIVE SILVER HALIDE OR A COMPOUND WHICH REACTS WITH SILVER LAURATE OR SILVER CAPRATE TO FORM A PHOTOSENSITIVE SILVER HALIDE, C. A REDUCING AGENT, D. A BINDER, AND E. A TONING AGENT REPRESENTED BY THE FORMULA:   WHEREIN R1, R2, R3 and R4 each represents a hydrogen atom, an alkyl group, an alkoxy group, an aryl group, an acylamido group, a halogen atom, a hydroxyl group or a nitro group.

United States Patent [1 1 Sashihara et al.

[ 51 May 27, 1975 THERMALLY DEVELOPABLE LIGHT-SENSITIVE ELEMENT [73] Assignee: Fuji Photo Film Co., Ltd.,

Kanagawa, Japan [22] Filed: May 7, 1974 [21] Appl. No.: 467,763

[30] Foreign Application Priority Data May 7, 1973 Japan 48-50427 [52] US. Cl. 96/67; 96/52; 96/109; 96/114.1;96/114.6 [51] Int. Cl. G03c 1/02; G03c 1/06 [58] Field of Search 96/109, 114.1, 52, 114.6, 96/67 [56] References Cited UNITED STATES PATENTS 3,080,254 3/1963 Grant, Jr 96/1 14.1

FOREIGN PATENTS OR APPLICATIONS 1,069,367 5/1967 United Kingdom 96/52 X 1,160,419 8/1969 United Kingdom 96/52 X Primary ExaminerNorman G. Torchin Assistant Examiner-Alfonso T. Suro Pico Attorney, Agent, or FirmSughrue, Rothwell, Mion, Zinn & Macpeak 57 ABSTRACT A lightsensitive element for heat development comprising a support having at least one layer thereon comprising;

a. silver laurate or silver caprate,

b. a catalytic amount of a photosensitive silver halide or a compound which reacts with silver laurate or silver caprate to form a photosensitive silver halide,

c. a reducing agent,

(1. a binder, and

e. a toning agent represented by the formula:

12 Claims, N0 Drawings 1 THERMALLY DEVELOPABLE LIGHT-SENSITIVE ELEMENT BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to lightsensitive elements for heat development and, more particularly, to lightsensitive elements for heat development which provide an image of blackish tone.

2. Description of the Prior Art A photographic method using silver halide has been widely used since a photographic method is superior to an electrophotographic method and a diazo method in sensitivity, gradation and the like. A silver halide photosensitive materials as used in the photographic method is developed with a developer after imagewise exposure and the image so developed is subjected to treatments such as stopping, fixing, washing or stabilization so that the material is protected from discoloration and fading due to ordinary rays and so that a nondeveloped portion is protected from blackening.

Therefore, problems arise in that the treatment requires a long time and much labor, the chemicals are harmful to the human body; and the chemicals soil the clothes and hands of operators in the treating room. Thus, it is desired that the lightsensitive element for use in the photographic method using silver halide be treated in a dry condition without employing a solution treatment and that the image so treated can be rendered stable.

Various attempts have been made to attain this purpose. For instance, a lightsensitive element containing mainly silver salts of higher aliphatic carboxylic acids such as silver behenate, silver saccharins saccharin, silver benzotriazole or the like, and further containing a catalytic amount of silver halide, is disclosed in U.S. Pat. Nos. 3,152,904, 3,457,075, 3,635,719, 3,645,739, and 3,756,829 and British Pat. No. 1,163,187.

Conventional photosensitive materials for heat devel opment, for example, a composition comprising an aliphatic acid silver salt, a reductant, and a catalytic amount of silver halide provides an image of a brownish tone when developed by heating after imagewise exposure. Therefore, the contrast between an image portion and a non-image portion is low and the image is difficult to read. Thus, a deep and blackish tone color image is desired in order to enhance the contrast.

Hitherto, silver salts of higher aliphatic acids such as silver behenate and silver stearate, silver benzotriazole, and silver saccharin have been considered suitable for an image forming compound. However, a large amount of solvent and a large scale apparatus are required to produce a large amount of silver salts such as silver behenate and silver stearate at one time since the behenic acid or behenic acid salt and the stearic acid or stearic acid salt starting material have low solubility in solvents such as water, methanol, and the like, which results in considerably increased costs. Silver benzotriazole and silver saccharin also increase the cost since the benzotriazole and saccharin starting materials are more expensive than aliphatic acids, and they are not as excellent in photographic properties. Thus, it is desired that aliphatic acid silver salts be employed.

Higher aliphatic acid silver salts such as silver behenate, silver stearate, and the like have the above described defects while silver salts of aliphatic acids having a very low member of carbon atoms such as silver acetate tend to gradually blacken by exposure because they are photosensitive.

Thus, it has been found that silver laurate and silver caprate are the most suitable. The silver salts of aliphatic acids higher than lauric acid have the same defects as silver behenate and the like while silver salts of aliphatic acids lower than capric acid are not preferred in that they have the defects to light the same as silver acetate and in that the aliphatic acids have a bad odor. Furthermore, it has been found that the stability of silver laurate to light can be improved by improving the method of preparation and the composition thereof although Japanese Pat. publication No. 4924/1968 describes that silver laurate is not stable to light. The same is true with silver caprate.

Incidentally, US. Pat. Nos. 3,080,254 and 3,107,174 describe that phthalazinone is an effective toning agent. It has been found, however, by experiments that phthalazinone is effective only for silver behenate and silver stearate, but is not effective for silver laurate and silver capr'ate as used herein. That is, an image prepared using a combination of silver laurate or silver caprate and phthalazinone has a brownish tone color. Therefore, it is desirable to find toning agents effective for silver laurate or silver caprate because they have the above described advantages.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide lightsensitive elements for heat development in which silver laurate or silver caprate is used.

It is another object of the present invention to provide photosensitive members which provide an image of a blackishtone when subjected to heat development.

The above objects and advantages of the present invention willbe apparent from the following detailed description.

This invention provides a photosensitive material for a thermally developable lightsensitive element which comprises:

a. a silver salt component comprising silver laurate or silver caprate,

b. a catalytic amount of a photosensitive silver halide component comprising a photosensitive silver halide, or a compound which reacts with silver laurate or silver caprate to form a photosensitive silver halide,

c. a reducing agent,

d. a binder, and

e. a toning agent comprising a compound represented by the formula:

wherein R R R and R each represents a hydrogen atom, an alkyl group, an alkoxy group, an aryl group,

an acylamido group, a halogen atom, a hydroxyl group or a nitro group.

DETAILED DESCRIPTION OF THE INVENTION Lightsensitive elements for heat development of the present invention comprise a support having at least one layer on the support, the layer comprising (a) a silver salt component comprising silver laurate or silver caprate, (b) a catalytic amount of a photosensitive silver halide component comprising one or more photosensitive silver halides, or one or more compounds which react with silver laurate or silver caprate to form a photosensitive silver halide, (c) a reducing agent component comprising one or more reductants, (d) a binder component comprising one or more binders, and (e) a toning agent component comprising one or more compounds represented by the formula:

wherein R,, R R and R are a hydrogen atom, an alkyl group (for example, an alkyl group having 1 to 4 carbon atoms such as methyl, ethyl, propyl, n-butyl, and tert-butyl is preferred), an alkoxy group (for example, having 1 to 4 carbon atoms such as methoxy, ethoxy, and the like is preferred), an aryl group (for example, phenyl, tolyl, and the like is preferred), an acylamido group (for example, having 1 to 4 carbon atoms such as acetamido and propionamide is preferred), a halogen atom (e.g., chlorine, bromine, and iodine), a hydroxyl group or a nitro group.

A preferred toning agent component comprises a compound represented by the formula wherein R R R and R, each is a hydrogen atom, a lower alkyl group having 1 to 4 crabon atoms, a methoxy group, a phenyl group, an acetamido group, a chlorine atom, a bromine atom, an iodine atom, a hydroxy group or a nitro group.

Representative examples represented by the above formula are l,3-benzoxazine-2,4-dione, 6-chloro-l,3- benzoxazine-2,4-dione, 6-bromol ,3-benzoxazine-2,4- dione, 6-iodo-1,3-benzoxazine-2,4-dione, 6-methyl- 1,3-benzoxazine-2,4-dione, 6-phenyl-1,3-benzoxazine- 2,4-dione, 6-nitro-1,3-benzoxazine-2,4-dione, 6- hydroxy-l ,3-benzoxazine-2,4-dione, 7-acetamidel ,3- benzoxazine-2,4-dione, 7-iodol ,3-benzoxazine-2,4- dione, 7-methyl-1,3-benzoxazine-2,4-dione, 7-tertbutyl-l ,3-benzoxazine-2,4-dione, 7-nitro-1,3-benzoxazine-2,4-dione, 7-hydroxy-1,3-benzoxazine-2,4-dione, 7-chloro-1,3-benzoxazine-2,4-dione, 8-methyl-l ,3- benzoxazine-2,4-dione, 8-phenyll ,3-benzoxazine-2,4- dione, 8-nitro-l ,3-benzoxazine-2,4-dione, 5,7- dimethoxy-S-chloro- 1 ,3-benzoxazine-2,4-dione, 5,7- dimethoxy-6,8-dichloro'- l ,3-benzoxazine-2,4-dione, 6,8-dibromo-l,3-benzoxazine-2,4-dione, 6,8-diiodo- 1,3-benzoxazine-2,4-dione, 6,8-dinitro-1,3-benzoxazine-2,4-dione, 7,8-dimethyll ,3-benzoxazine-2,4- dione and the like.

These compounds can be prepared in accordance with the methods described in the following literature references: J. Am. Chem. Soc., 79, 2811-14 (1957); Pharmazie, 21 (3), 161-6 1966); Yakugaku Zashi, 82, 1426-30 (1962); Pharm. Zentralhalle, 103 (11-12), 791-8 (1964); Bull. Soc. Chim. France, 1966 (8), 2525-9; Ann. Chim., 57 (6), 607-15 (1967); and British Pat. No. 1,160,419.

The amount of the toning agent component (e) as used herein can range from about 1 X 10 to about 1 mole per mole of the silver salt component (a) and preferably ranges from about 2 X 10' to about 1 X 10 mole per mole of the silver salt component (a).

The photosensitive silver halide component (b) is 1) compounds which react with the silver salt component (a) to form a silver halide, or (2) a silver halide. Representative examples of the former (l) are inorganic compounds of the formula:

wherein M is a hydrogen atom, an ammonium group, or a metal atom (for example, strontium, cadmium, zinc, tin, chromium, sodium, barium, iron, cesium, lanthanum, copper, magnesium, potassium, aluminum, antimony, gold, cobalt, mercury, lead, beryllium, lithium, manganese, gallium, indium rhodium, ruthenium, palladium, iridium, platinum, thallium, bismuth and the like; X is a halogen atom (e.g., chlorine, bromine and iodine); and n is 1 when M is a hydrogen atom or an ammonium group while when M is a metal atom, n is equal to valence of the metal.

The above described compounds (1) further include organic halogen compounds such as triphenylmethyl chloride, triphenylmethyl bromide, 2-bromo-2-methyl propane, 2-bromobutyrate, 2-bromoethanol, benzophenone dichloride, iodoform, bromoform, carbon tetrabromide, N-haloacetamide, an N-halosuccinimide, an N-halophthalimide, an N-halophthalazone, an N- halobenzotriazole, an N-halobenzimidazole, 1,3- dibromo-S ,S-dimethylthiohydantoin. l ,3-dichloro-5,5- dimethyl thiohydantoin, onium halide and the like. These compounds are disclosed in Japanese Pat. application No. 126658/73, and Us. Pat. No. 3,679,422.

As silver halides of the latter (2), silver chloride, silver bromide, silver bromide iodide, silver chloride bromide iodide, silver chloride bromide and silver iodide are exemplary.

An emulsion containing a photosensitive silver halide can be prepared using any method known in the art of photography. For instance, the emulsion can be an emulsion prepared by the single jet process; prepared by the double jet process such as a Lipman emulsion; an ammonia process emulsion; a thiocyanate or thioether maturing emulsion such as those as disclosed in U.S. Pat. Nos. 2,222,264, 3,320,069 and 3,271,157.

The silver halides as used herein can be sensitized using conventional chemical sensitizers for silver halides such as reductants, sulfur or selenium compounds, gold, platinum or palladium compounds, or mixtures thereof. Suitable methods are described, for example, in U.s. Pat. Nos. 2,623,499, 2,399,083, 3,297,447 and 3,297,446.

The compounds of the photosensitive silver halide component (b) can be used alone or in combination with each other. The amount of the photosensitive silver halide component (b) which can be suitably used ranges from about 0.001 to 0.5 mole, preferably 0.005 to 0.3 mol, per mole of the silver salt component (a). The use of component (b) below the lower limit results in a low sensitivity while the use of too large an amount of the component (b) results in a gradual blackening of a non-image portion when the developed member is allowed to stand under ordinary illumination, resulting in a deterioration of the contrast between the image portion and the non-image portion.

The reducing agent component which can be used herein must be suitable for forming a silver image by reducing the silver salt component (a) when heated in the presence of exposed silver halide. Suitable reductants include substituted phenols, substituted or unsubstituted bisphenols, hydroquinone monoethers and the like. Representative examples of these compounds are 1,4-bis-(4-hydroxyphenyl)cyclohexane, 1,1-bis-(5- chloro-2-hydroxyphenyl )methane, l,1-bis-(5-chloro-2- hydroxyphenyl)ethane, diethylstilbestrol, hexestrol, 2,- 2-bis-(3,5-dibromo-4-hydroxyphenyl)-propane, 2,2- bis-(4-hydroxyphenyl)propane, a-phenyl-o-cresol, hydroquinonemonobenzyl ether, p-nonylphenol, p-

octylphenol, p-ethylphenol, p-sec-butylphenol, p-tamylphenol, p-acetylphenol, 2-acetoacetyl-4- methylphenol, 1-(2-quinolyl)-3-methyl-5-pyrazolone, 1-chloro-2,4-dihydroxybenzene, 3 ,5-di-t-butyl-2 ,6- dihydroxybenzoic acid, 2,4-dihydroxybenzoic acid, resorcin, 2,4-dihydroxyphenylsulfide, 5,7-dihydroxy-4- methylcumarin, p-methoxyphenol, 2-tert-butyl-4- methoxyphenol, p-phenylphenol, p-t-butylphenol, 2-tbutyl-p-cresol, l3-naphthol, 2,4,5-tri-methylphenol, 2,5- di-t-butyl-4-methoxyphenol, hydroquinone mono-npropyl ether, hydroquinone mono-n-hexyl ether, 2,3- dimethylphenol, 2,4-di-t-butylphenol, N,N-di(4- hydroxyphenyl)ureaand the like.

Two or more reducing agents can be used simultaneously if desired.

The amount of the reducing agent component (c) as used herein generally ranges from about 0.1 to 5 mole, preferably 0.5 to 2 mole, per mole of the silver salt component (a).

The component (a), (b), (c), and (e) are dispersed in the binder component (d) and the resulting dispersion is coated on a support to form a layer. A part or all of the layer can be composed ofa plurality oflayers. The binders which can be used herein include any known binders used in the art. It is generally preferred that the binder be hydrophobic, but the binder can be hydrophilic. They can be transparent or translucent and include both naturally-occurring substances such as proteins, for example, gelatin, gelatin derivatives such as phthaloylated gelatin, etc., cellulose derivatives such as cellulose acetate butyrate, cellulose acetate propionate, etc., polysaccharides such as dextran, gum arabic and the like; and synthetic polymeric substances such as water-soluble polyvinyl compounds like poly- (vinyl pyrrolidone), acrylamide polymers and the like. Other synthetic polymeric compounds which can be rylates or methacrylates, and those which have cross- I linking sites which facilitate hardening or curing as well as those having recurring sulfobetaine units as described in Canadian Pat. No. 774,054. Preferred high molecular weight materials and resins include polyvinyl butyral, cellulose acetate butyrate, polymethyl methacrylate, poly(viny1 pyrrolidone), ethyl cellulose, polystyrene, polyvinyl chloride, chlorinated rubber, polyisobutylene, butadiene-styrene copolymers, vinyl chloride-vinyl acetate copolymers, copolymers of vinyl acetate, vinyl chloride and maleic acid and polyvinyl alcohol. If desired, two or more binders selected from the above compounds can be used.

The weight ratio of the binder component (d) to the silver salt component (a) suitably is in the range of about 10:1 to 1:10, preferably 4:1 to 1:4.

As the support, various kinds of supports can be employed. Typical supports include cellulose nitrate films, cellulose ester films, polyvinyl acetate films, polystyrene films, polyethylene terephthalate films, polycarbonate films, glass, paper, metal, and the like. A support paper treated to render it hydrophilic can be employed when an organic solvent is used in a emulsion layer. A paper sized with polysaccharides can also be used.

The amount of the silver of the silver salt (a) in the above binder dispersion coated on the substrate suitably can range from about 0.2 to 3 g/m and preferably from 0.4 to 2 g/m When the amount coated is below 0.2 g/m sufficient image density cannot be obtained and more than 3 g/m leads to high cost. The necessary amount of the silver laurate or silver caprate which is used as component (a) is determined by the amount of silver coated.

To the lightsensitive element for heat development, an antistatic layer or an electrically conductive layer can be provided. Suitable antistatic layers or electrically conductive layers, can include soluble salts such as halide compounds, nitrates, vapor deposited metal layers, ionic polymers as disclosed in U.S. Pat. Nos. 2,861,056 and 3,206,312 or insoluble inorganic salts as disclosed in U.S. Pat. No. 3,428,451. Antihalation materials or dyes can also be included if desired.

The photosensitive material of the present invention, if desired, can contain matting agents such as starch, titanium dioxide, zinc oxide and silica. Moreover, the material can contain fluorescent brightening agent such as stilbenes, triazines, oxazoles, and a coumarin fluorescent brightening agent.

The photosensitive layer for heat development as used in the practice of the present invention can be coated by various coating methods such as a dipping method, an air knife method, a curtain coating method or an extrusion coating method as described in U.S. Pat. No. 2,681,294 wherein a hopper is used. If desired, two or more layers can be coated simultaneously.

some of optical sensitizing dye effective for conventional silver halide emulsions can be advantageously used to provide enhanced photosensitivity to the photosensitive material of the present invention.

For instance, optical sensitization can be carried out by adding sensitizing dyes in the form of a solution or dispersion thereof. Optical sensitizers which can be used herein include the cyanines, merocyanines, complex (trinuclear or tetranuclear) cyanines, homopolar cyanines, styryls, hemicyanines such as enamine, oxonols and hemioxonols. Dyes of the cyanine classes can contain such basic nuclei as the thiazolines, oxazolines, pyrrolines, pyridines, oxazoles, thiazoles, selenazoles, and imidazoles. Such nuclei can contain alkyl, alkylene, hydroxyalkyl, sulfoalkyl, carboxyalkyl, aminoalkyl, and enamine groups that can be fused to carbocyclic or heterocyclic ring systems etiher unsubstituted or substituted with halogen atoms and/or phenyl, alkyl, haloalkyl, cyano, or alkoxy groups. The dyes can be symmetrical or unsymmetrical and can contain alkyl, phenyl, enamine or heterocyclic substituents on the methine or polymethine chain.

The merocyanine dyes can contain the basic nuclei described as well as acid nuclei such as thiohydantoins, rhodanines, oxazolidenediones, thiazolidenediones, barbituric acids, thiazolineones, and malononitrile. These acid nuclei can be substituted with alkyl, alkylene, phenyl, carboxyalkyl, sulfoalkyl, hydroxyalkyl, alkoxyalkyl, alkylamine groups or heterocyclic nuclei. Combinations of these dyes can be used if desired. In addition, supersensitizing addenda which do not absorb visible light can be included such as, for instance, ascorbic acid derivatives, azaindenes, cadmium salts, and organic sulfonic acid as described in U.S. Pats. Nos. 2,933,390, and 2,937,089. Especially, effective dyes which can be used in the heat-developable material of this invention, are merocyanine dyes which have a rhodanine, thiohydantoin, or 2-thio-2,4-oxazolidinedione nucleus, such as 3-p-carboxyphenyl-5-[[3-(3- ethyl-2(3)-benzoxazolylidene)ethylidene]rhodanine, 5-[(3-B-carboxyethyl-2(3)- thiazolinylidene)ethylidene]-3-ethyl-rhodanine, carboxymethyl-5-[ p-( 3-methylthiazolinylidene )-aethylethylidene rhodanine, l-carboxymethyl-5-[ 3- ethyl-2(3H)-benzoxazolylidene]-3-phenyl-2- thiohydantoin, 5-[(3-ethyl-2-benzoxazolinylidene)-lmethyl-ethylidene]-3-[3-(3-pyrrolin- 1- yl)propyl]rhodanine, 3-carboxymethyl-5-[(3-methyl- 2( 3H )-thiaz0linylidene )isopropylidene rhodanine, and the trinuclear merocyanine dyes as disclosed in Us. Pat. No. 3,719,495, the multi-ring aromatic dyes as dis closed in Belgian Pat. No. 788,695, the dyes as disclosed in Japanese Pat. application No. 56332/72, the styrylquinonine dyes as disclosed in Japanese Pat. application No. 127999/72, the rhodacyanine dyes as disclosed in Japanese Pat. application No. 14916/73, and acid dyes such as 2', 7"dichlorofluoroscein as disclosed in Japanese Pat. applications 7624/73, 12587/73, 50903/73 and 81550/73. The amount of the dye as used ranges from about 1 X 10 to l X 10 mole, preferably 1 X 10' to l X 10 mole, per mole of silver salt of the silver salt component (a).

The photosensitive layer for heat development preferably contains an antiheatfogging agentv The antiheatfogging agent prevents the non-exposed portion of the lightsensitive element from being affected by heat development. Examples of antiheatfogging agents include N-halo compounds such as the N-haloacetamides, for example, N-bromoacetamide, N-iodoacetamide and N-chloroacetamide; the N-halosuccinic imides, for example, N-bromosuccinic imide, N-iodosuccinic imide, and N-chlorosuccinic imide; lithium compounds such as lithium carboxylates, for example, lithium laurate, and the compounds as disclosed in Japanese Pat. application No. 8194/1973. The antiheatfogging agent is preferably used in the range of from about 1 X 10 mole, preferably 1 X 10 to 1 mole, per mole of the silver salt component (a).

In order to increase the transparency of the photosensitive layer for heat development, to increase the image density, and to improve the storage stability (which indicates that the photographic properties of a newly prepared lightsensitive element are not changed after a certain period of storage), an overlying polymer layer can be provided on the photosensitive layer. The thickness of the overlaying layer suitably ranges from about 1 to 20 u. Representative examples are polyvinyl chloride, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, polyvinyl butyral, polystyrene, polymethyl methacrylate, polyurethane rubber, xylene resin, benzyl cellulose, ethyl cellulose; cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, polyvinylidene chloride, chlorinated polypropylene, polyvinyl pyrrolidone, cellulose propionate, polyvinyl formal, cellulose acetate phthalate, polycarbonate, cellulose acetate propyonate and the like.

It is more desirable that the overlying layer contains kaolin since a kaolin containing layer can be written with a pencil and the like after the formation of the image.

The above described lightsensitive element for heat development can be developed simply by heating after exposure to radiation from a light source such as a xenon lamp, a tungsten lamp, a mercury lamp and the like. Suitable heating temperatures range from about to 160C and preferably to C. Higher temperatures or lower temperatures can be employed within the above range by prolonging or shortening the heating period. The developing period of time is generally from about one second to 60 seconds.

There are various methods for heat-developing the light-sensitive element of the present invention. For instance, the lightsensitive element can be brought in contact with a simple heating plate or a heated drum and in some cases, it can be passes through a heated atmosphere. Moreover, it can be heated using high frequency heating or a laser beam.

The photosensitive member of the present invention, when subjected to developing treatment, provides an image of a blackish tone. Thus, the maximum density is high and the constrast between an image portion and a non-image portion is distinct.

The present invention will be further illustrated by reference to the following examples. Unless otherwise indicated, all parts, percents, ratios and the like are by weight.

EXAMPLE 1 To a solution prepared by dissolving 8.6 g of capric acid in 100 ml of isoamyl acetate was added 50 ml of an aqueous silver ammonium complex solution (cooled to 50C) containing 8.5 g of silver nitrate over a period of 30 seconds while maintaining the temperature at 5C and stirring with a stirrer to react the capric acid with the silver ion. Crystals of silver caprate in the form of spindles of about 3 pt X 0.2 ,u. in size were obtained. The

thus-obtained silver salt was washed with water and then with methanol. Then, 2.1 g of this silver salt, 3.0 g of polyvinyl butyral, and 20 ml of isopropyl alcohol were dispersed in a ball mill to prepare a polymer dispersion of the silver salt.

To 20 g of the polymer dispersion of the silver salt were added the following ingredients to prepare a photosensitive coating liquid for heat development, which was coated on a paper support in an amount of 1.0 g of silver per square meter of the support to form a lightsensitive element for heat development (A).

For comparison, a lightsensitive element (B) was prepared without adding the toning agent of the present invention, and a photosensitive member (C) was prepared using an equal amount of phthalazinone in place of the toning agent of the present invention.

After applying an exposure amount of 1 X lux-sec using tungusten light source (using a step wedge), the lightsensitive elements (A), (B), and (C) were developed and step images were obtained.

On observing the thus-obtained images visually, the light-sensitive element (A) had a blackish tone with a maximum density of 1.5 and the lightsensitive elements (B) and (C) had a brownish tone. Particularly, with the lightsensitive element (B) in which the toning agent was not used, only an image of a brownish tone having a maximum density of 0.4 was obtained.

EXAMPLE 2 The procedure of Example 1 was repeated except that 8-methyl-l,3-benzoxazine-2,4-dione was used in place of l,3-benzoxazine-2,4-dione in an equal amount, and a black image having a maximum density of 1.3 was obtained.

EXAMPLE 3 To a solution prepared by dissolving 11 g of lauric acid in 100 ml of butyl acetate was added 100 ml of a diluted aqueous solution of nitric acid (at 25 C, pH=2.0) while maintaining the temperature at 10C and stirring with a stirrer to form a mixture. Then, 50 ml of an aqueous silver ammonium complex solution (cooled to 0C) containing 8.5 g of silver nitrate was added to the mixture over a period of 1 minute while stirring to react the lauric acid with the silver ion.

Crystals of silver laurate in the form of spindles of a size of about l p. X 0.05 ,u. were obtained and the crystals were washed with water and additionally with methanol. Then, 2.7 g of silver laurate, 3.0 g of polyvinyl butyral, and 20 ml of isopropyl alcohol were dispersed in a ball mill to prepare a polymer dispersion of the silver salt.

To 20 ml of the polymer dispersion of the silver salt were added the following ingredients to prepare a photoning agent of the present invention, and a lightsensitive element (C) was prepared using phthalazine.

Ammonium Bromide (2.5% by weight methanol 1 ml solution; silver halide forming compound of the component (b) cellosolve; antiheatfogging agent) On the photosensitive layers of the thus prepared lightsensitive elements (A), (B), and (C) was coated a 5 percent by weight acetone solution of cellulose diacetate to form a dry film of a thickness of 10 1..

After applying an exposure amount of 5 X 10 lux-sec using a tungusten light source (using a step wedge), the lightsensitive elements (A), (B), and (C) were developed by heating at C for 20 seconds. With the lightsensitive element (A), an image of a blackish tone having a maximum density of 1.4 was obtained, and with the lightsensitive elements (B) and (C yellow brown images having a maximum density of 0.4 were obtained.

EXAMPLE 4 The procedure of Example 3 was repeated except that 8-methyl-l,3-benzoxazine-2,4-dione was used in place of l,3-benzoxazino-2,4-dione in an equal amount. On applying the same developing treatment as described in Example 3, a black image having a maximum density of 1.3 was obtained.

EXAMPLES 5 11 On repeating the procedure of Example 3 except that the following compounds were used in place of 1,3-benzoxazine-2,4-dione in an equal amount, images of a blackish tone were obtained.

Example 5 6-Chloro-l,3-benzoxazine-2,4-dione Example 6 6-Phenyl-l ,3-benzoxazine-2,4-dione Example 7 6-Hydroxy-l,3-benzoxazine-2,4-dione Example 8 6-Iodo-1,3-benzoxazine-2,4-dione Example 9 6-Nitro-1,3-benzoxazine-2,4-dione Example 10 5 ,7-Dimethoxy-6,8-dichloro-1 ,3-

benzoxazine-2,4-dione Example 1 1 7-tert-Butyl-l,3-benzoxazine-2,4-dione.

While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.

What is claimed is:

l. A photosensitive material for a thermally developable lightsensitive element which comprises:

a. s silver salt component comprising silver laurate or silver caprate,

b. a catalytic amount of a photosensitive silver halide component comprising a photosensitive silver halide, or a compound which reacts with silver laurate or silver caprate to form a photosensitive silver halide,

c. a reducing agent,

(1. a binder, and

e. a toning agent comprising a compound represented by the formula:

wherein R R R and R each represents a hydrogen atom, an alkyl group, an alkoxy group, an aryl group, an acylamido group, a halogen atom, a hydroxy] group or nitro group.

2. A thermally developable lightsensitive element comprising a support having thereon at least one layer comprising:

a. a silver salt component comprising silver laurate or silver caprate;

b. a catalytic amount of a photosensitive silver halide component comprising a photosensitive silver halide, or a compound which reacts with the silver laurate or silver caprate of silver salt component (a) to form a photosensitive silver halide;

. a reducing agent;

i a binder; and

. a toning agent component comprising a compound represented by the formula:

(UG Y) wherein R R R and R each represent a hydrogen atom, an alkyl group, an alkoxy group, an aryl group, an acylamido group, a halogen atom, a hydroxy] group, or a nitro group.

3. The lightsensitive element according to claim 2, wherein said photosensitive silver halide is silver chloride. silver bromide. silver bromide iodide, silver chlo :ride bromide iodide, silver chloride bromide, or silver iodide.

4. The lightsensitive element according to claim 2, wherein the compound which reacts with silver laurate or silver caprate to form a photosensitive silver halide is selected from the group consisting of an inorganic compound represented by the formula:

wherein M is a hydrogen atom, an ammonium group or a metal atom, X is a halogen atom, and n is 1 when M is a hydrogen atom or an ammonium group and when M is a metal atom, n is equal to the valence of the metal. and an organic halogen compound.

5. The lightsensitive element according to claim 4, wherein the organic halogen compound is triphenylmethyl chloride, triphenylmethyl bromide, 2-bromo-2- methyl propane, 2-bromobutyrate, 2-bromoethanol, benzophenone dichloride, iodoform, bromoform, carbon tetrabromide, an N-haloacetamide, an N- halosuccinimide, an N-halophthalimide, an N- halophthalazone, an N-halobenzotriazole, an N- halobenzimidazole, l,3-dibromo-5,S-dimethylthiohydantoin, l,3-dichloro-5,5-dimethyl thiohydantoin or an onium halide.

6. The lightsensitive element according to claim 2, wherein the amount of the photosensitive silver halide component (b) ranges from about 0.001 to 0.3 mole per mole of the silver salt component (a).

7. The lightsensitive element according to claim 2, wherein the reducing agent is a substituted phenol, a substituted or unsubstituted bisphenol or a hydroquinone monoether.

8. The lightsensitive element according to claim 2, wherein the amount of the reducing agent Component (c) ranges from about 0.5 to 2 mole per mole of the silver salt component (a).

9. The lightsensitive element according to claim 2, wherein the weight ratio of the binder component (d) to the silver salt component (a) ranges from about 4:1 to 1:4.

10. The lightsensitive element according to claim 2, wherein the toning agent component comprises a compound represented by the formula wherein R,, R R and R each is a hydrogen atom, a lower alkyl group having 1 to 4 carbon atoms, a methoxy group, a phenyl group, an acetamido group, a chlorine atom, a bromine atom, an iodine atom, a hydroxy group or a nitro group.

11. The lightsensitive element according to claim 2, wherein the layer further contains at least one optical sensitizer in an amount of from about 1 X 10' to about l X 1O- mole per mole of the silver salt component 12. The lightsensitive element according to claim 2, wherein the layer further contains at least one antiheatfogging agent in an amount of from about 1 X 10 to 1 mole per mole of the silver salt component (a). 

1. A PHOTOSENSTIVE MATERIAL FOR A THERMALLY DEVELOPABLE LIGHTSENTIVE ELEMENT WHICH COMPRISES: A. A SILVER SALT COMPONENT COMPRISING SILVER LAURATE OR SILVER CAPRATE, B. A CATALYTIC AMOUNT OF A PHOTOSENSITIVE SILVER HALIDE COMPONENT COMPRISING A PHOTOSENSITIVE SILVER HALIDE, OR A COMPOUND WHICH REACTS WITH SILVER LAURATE OR SILVER CAPRATE TO FORM A PHOTOSENSITIVE SILVER HALIDE, C. A REDUCING AGENT, D. A BINDER, AND E. A TONING AGENT COMPRISING A COMPOUND REPRESENTED BY THE FORMULA:
 2. A thermally developable lightsensitive element comprising a support having thereon at least one layer comprising: a. a silver salt component comprising silver laurate or silver caprate; b. a catalytic amount of a photosensitive silver halide component comprising a photosensitive silver halide, or a compound which reacts with the silver laurate or silver caprate of silver salt component (a) to form a photosensitive silver halide; c. a reducing agent; d. a binder; and e. a toning agent component comprising a compound represented by the formula:
 3. The lightsensitive element according to claim 2, wherein said photosensitive silver halide is silver chloride, silver bromide, silver bromide iodide, silver chloride bromide iodide, sIlver chloride bromide, or silver iodide.
 4. The lightsensitive element according to claim 2, wherein the compound which reacts with silver laurate or silver caprate to form a photosensitive silver halide is selected from the group consisting of an inorganic compound represented by the formula: M Xn wherein M is a hydrogen atom, an ammonium group or a metal atom, X is a halogen atom, and n is 1 when M is a hydrogen atom or an ammonium group and when M is a metal atom, n is equal to the valence of the metal, and an organic halogen compound.
 5. The lightsensitive element according to claim 4, wherein the organic halogen compound is triphenylmethyl chloride, triphenylmethyl bromide, 2-bromo-2-methyl propane, 2-bromobutyrate, 2-bromoethanol, benzophenone dichloride, iodoform, bromoform, carbon tetrabromide, an N-haloacetamide, an N-halosuccinimide, an N-halophthalimide, an N-halophthalazone, an N-halobenzotriazole, an N-halobenzimidazole, 1,3-dibromo-5,5-dimethylthiohydantoin, 1,3-dichloro-5,5-dimethyl thiohydantoin or an onium halide.
 6. The lightsensitive element according to claim 2, wherein the amount of the photosensitive silver halide component (b) ranges from about 0.001 to 0.3 mole per mole of the silver salt component (a).
 7. The lightsensitive element according to claim 2, wherein the reducing agent is a substituted phenol, a substituted or unsubstituted bisphenol or a hydroquinone monoether.
 8. The lightsensitive element according to claim 2, wherein the amount of the reducing agent component (c) ranges from about 0.5 to 2 mole per mole of the silver salt component (a).
 9. The lightsensitive element according to claim 2, wherein the weight ratio of the binder component (d) to the silver salt component (a) ranges from about 4:1 to 1:4.
 10. The lightsensitive element according to claim 2, wherein the toning agent component comprises a compound represented by the formula
 11. The lightsensitive element according to claim 2, wherein the layer further contains at least one optical sensitizer in an amount of from about 1 X 10 6 to about 1 X 10 2 mole per mole of the silver salt component (a).
 12. The lightsensitive element according to claim 2, wherein the layer further contains at least one antiheatfogging agent in an amount of from about 1 X 10 3 to 1 mole per mole of the silver salt component (a). 